1. Technical Field
This invention relates generally to radio controlled (R/C) models, and more particularly to a control system enabling more effective operator control of the R/C model's drive motor.
2. Description of Related Art
The battery powered drive motor of a conventional R/C model operates under control of an R/C model control system. The control system includes an onboard speed control module (or speed controller), a miniature onboard receiver, and a separate handheld transmitter unit. An R/C enthusiast manipulates a throttle/brake trigger on the transmitter unit to input speed and braking setpoint information, the transmitter unit communicates that information to the speed controller via the onboard receiver, and the speed controller controls the drive motor accordingly.
A typical throttle/brake trigger (or other moveable member for inputting speed and braking setpoint information) normally occupies a neutral position representing zero speed and no braking. Pulling the trigger from the neutral position in a first direction increases motor speed and pushing it from neutral in a second direction increases braking. The operator simply places a finger through a loop in the trigger, pulls on it to increase speed, and pushes on it to increase braking.
Different positions in the first direction (the throttle side of neutral) represent different speed setpoints for different drive motor speeds, increasing from little speed at an initial setpoint position nearest the neutral position to maximum speed at a maximum-speed setpoint position furthest the neutral position. Similarly, different trigger positions in the second direction (the brake side of neutral) produce different braking setpoints representing different braking rates, increasing from little braking at an initial-braking setpoint position nearest the neutral position to maximum braking at a maximum-braking setpoint position of the trigger furthest the neutral position. So, by skillfully pushing and pulling on the trigger, the operator can control the motor with sufficient finesse to undertake complex maneuvers with the R/C model and even successfully engage in racing activities.
However, existing control systems produce an uneven drive motor response to trigger movement. On the throttle side of neutral, incremental changes in trigger position near neutral (low speeds) cause greater changes in motor speed than do similar changes in trigger position near the maximum-speed position (high speeds). In other words, the drive motor is very sensitive to trigger operation near the neutral position and less sensitive near the maximum-speed setpoint position.
Conversely, an incremental change in trigger position near the neutral position on the brake side of neutral produces a smaller change in braking than it does near the maximum-braking setpoint position. The trigger is less sensitive to trigger operation near the neutral position and more sensitive near the maximum-braking setpoint position.
R/C drive motor response at various speeds to a step response in excitation can cause those characteristics. They frustrate operation because the operator must continually compensate for trigger sensitivity according to trigger position while rapidly pushing and pulling on the trigger (e.g., 3 to 4 times per second). Failure to properly compensate can result in the drive wheels of the model spinning from too much forward torque when the operator pulls on the trigger to increase speed and locking from too much reverse torque when the operator pushes on the trigger to increase braking. Such undesired drive wheel responses can significantly impair maneuverability and even lose the race, and. existing control systems fail to account for drive motor characteristics resulting in such uneven throttle/brake trigger sensitivity. As a result, operators need an R/C model control system with improved control characteristics.